SPECTROSCOPIC STUDIES OF THE INTERACTION BETWEEN KOLAVIRON AND ALDEHYDE DEHYDROGENASE

Abstract

Aldehyde dehydrogenase (ALDH) is a superfamily of phase I oxidizing enzyme responsible for detoxification of biogenic and xenogenic aldehydes to the corresponding carboxylic acids by means of an NAD(P)+dependent reaction. The enzyme has been implicated in the protection of prokaryotic and eukaryotic organisms against various stress conditions. ALDH is also involved in non-enzymatic ligand binding to endobiotics and xenobiotics.Kolaviron, a biflavonoid, isolated from Garcinia kola (Bitter kola) molecular interaction with ALDH was investigated by steady state fluorescence and UV-Visible spectroscopies techniques under physiological conditions.Fluorescence spectra and data showed that kolaviron has a strong ability to quench the intrinsic fluorescence of ALDH through a mixture of static dynamic quenching procedure, and the effective quenching constant (Ksv) was 2.57x104 L. mol-1. The Scatchard plot indicated that Aldehyde dehydrogenase has onebinding sites for kolaviron with a binding constant (Ka) of 6.4x103 L.mol-1and a dissociation constant of 3.28x10-4L.mol-1 at 298K and pH 7.4 showing a strong bonding interaction of ALDH-kolaviron. The thermodynamic data suggest that kolaviron binding to ALDH was not spontaneous. Hydrophobic bondplayed a major role in the bindingat the pH of 7.4 and 5.0, and Van der Waal bond at the pH of 9.0. UV-Visible spectra of the ALDH-kolaviron complex showed unperturbed secondary structure but perturbed tertiary structure of ALDH by the ligand. There was no entropy-enthalpy compensation of ALDH-kolaviron interaction. The synchronous fluorescence of ALDH-Kolaviron indicated conformational change near the Tryptophan residue micro-environment rather than tyrosine.According to Forster non-radiation energy transfer theory, the binding of kolaviron to ALDH was of great probability of less than 8 nm. This work established a clear relationship between kolaviron and ALDH and has helped in understanding of the ligand binding properties of the enzyme and the dynamics and thermodynamics of their interactions.